He was recording with a mic in front of his humming guitar amp for about 30 seconds just to see what happened. After reviewing the tape, he found an interesting noise about 20 seconds in that was different than the very steady buzz of the amplifier. If you listen carefully it really does sound like a faint voice saying something.

Since he was curious he ran it through Adobe Audition audio software and amplified it and reduced some of the noise. The audio he captured made me jump out of my seat!

"How are you" the voice says. After going back to the original recording, I do believe I can hear that same phrase without amplification. Or my mind is playing tricks on me.